[Discuss] Backing up LVM partitions using snapshots

[blu at nedharvey.com (Edward Ned Harvey)]

> From: markw at mohawksoft.com [mailto:markw at mohawksoft.com]
> Sent: Sunday, December 11, 2011 2:48 PM
> 
> I will argue that an rsync will NEVER be more effective unless you
> actively wipe the blocks where a file once existed. 

for (( i=0 ; i<200 ; i++ )) ; do
mkdir temp
cp datafile temp
run_test $i >> testresults.txt
rm -rf temp
done

In this case, rsync is what you want, because it ignores files that don't
exist.  But a block level backup will backup all the blocks that were ever
contained in any of the (now removed) copies of the datafile.

I don't know what users you support, but I support engineers who run this
type of test all the time.  They create test work dirs, they perform
volatile work in there, store the results of the test, and remove their
scratch dir.

The block level backup you're talking about is great, under the assumption
that you basically just add data to a filesystem.  It's terrible when you
add & remove data from the filesystem.  I stand by my claim:  Important to
know if it's suitable for your purposes, whoever you are, the consumer who
might consider using this.